PRK and epi-LASEK

PRK,
or photorefractive keratectomy is a laser technique that treats the middle
layers of the cornea to correct hyperopia (farsightedness), myopia (nearsightedness) and astigmatism. The purpose of
PRK is to reshape the cornea to help the eye to focus at far distances, reducing, or in some
cases eliminating, the need for glasses or contact lenses.

The Procedure:

PRK is performed using topical anesthetic (eye drops that eliminate pain). Next, a
small spring-like device is inserted to help keep the eye open. Using a small hand
instrument, the front surface cells of the cornea are gently removed. This allows
access to the layers of the cornea that need to be treated by the laser.

The laser procedure is then performed
on the cornea. It is this "lasering" that
shapes the cornea for improved vision. The laser treatment lasts 30 to 90 seconds.
Afterwards, a contact lens is placed over the front surface of the cornea. This
contact lens acts as a bandage to help the cornea heal its front surface.

The entire procedure takes about 5 minutes to complete. Patients are typically amazed at the
comfort and speed of the procedure. Since the eye is completely
anesthetized, patients do not feel the instruments or the laser. However, some pressure
may be felt by a small spring device, which is used to help keep the eyelids open.

Postoperative Treatment:

Patients
are placed on antibiotic and anti-inflammatory eye drops to promote comfort, prevent
infection, and reduce inflammation. These drops are used four times a day initially and
tapered over a few days to a week. Follow-up examinations are scheduled daily until the
front surface of the eye heals (usually two to four days), then at one week, one month,
and three months postoperatively.

LASIK vs. PRK:

There is typically minimal discomfort in the first 1-2 days after LASIK, whereas PRK may
produce more discomfort or, in some instances, significant pain. Since none of the surface
tissues of the eye are removed in LASIK (as opposed to PRK), the eye remains protected by
its natural epithelial barrier. The only time it is not covered is when the flap is folded
over for the laser procedure, and when the thin edge of the flap is healing, which
normally takes a few hours after the laser procedure. In general, no contact lens is
necessary for LASIK healing. PRK, on the other hand, requires that the surface cells
(epithelium) be physically scraped off before the laser procedure is done. After the
excimer laser is used, the eye is fit with a bandage contact lens (like an eye
"Band-Aid" TM), and the epithelium regenerates. This takes two to four days,
depending on the eyes healing powers. The epithelial healing process can range from
mild discomfort to overt pain. Usually, the patient feels like he/she scratched her eye
putting a contact lens in. While topical (eye drop) pain medication can be used to
decrease the sensation, sometimes strong oral pain medications are necessary.

Typically, visual recovery is exceedingly quick for LASIK, generally within a few days.
Again, this is due to the fact that the eyes natural coverings are returned to their
original locations. Visual recovery for PRK, on the other hand, can take from 1-2 weeks to
months, depending on the amount of correction performed. For both procedures, the final
visual results are due to the effects of the laser procedure itself and the patient's own
healing patterns.

Since no two patients heal exactly alike, some variability in the final visual outcomes
can be expected, and sometimes retreatments (requiring further lasering) are necessary.
For retreatments with PRK, the surface cells have to be rescraped, with the associated
post lasering healing pain for two to four more days. With LASIK retreatments, on the
other hand, the ORIGINAL flap can be lifted and replaced with minimal patient discomfort.

When treating
greater degrees of myopia with PRK, more patient healing is required, and there is more
variability in results and more risk of abnormal healing in the form of surface haze (a
form of eye scarring that occurs with PRK). The inner layers of the cornea are far less
likely to react and rarely produce haze or scar tissue, making LASIK a more ideal
procedure for treating higher myopia.

LASIK introduces the risks of complications produced by the microkeratome;
these risks
are obviously not found with PRK.

Possible Complications:

As with any surgical procedure, complications can occur. Fortunately, the majority of
PRK complications are easily treated and have little effect on final visual outcome.
Postoperative complications in the short term can be associated with infections or
inflammation. These can usually be treated with antibiotics or steroids. Sometimes haze or
shifts in refraction may require the use of steroids. Fortunately, most haze
disappears, and shifts generally stabilize.

Activity:

There are minimal restrictions on activities following PRK. Exercise, watching TV,
reading, flying, and driving are all acceptable, as long as the patient feels up to it.
The major activity to be avoided is eye rubbing, which could possibly dislodge the contact
lens. Additionally, driving or operating heavy machinery should be avoided for a day or
two if sedatives (such as Valium) are used during the operation.

epi-LASEK

epi-LASEK, or laser epithelial keratomileusis, (not a misspelling of LASIK) is
simply a modified PRK procedure. It is not to be confused with LASIK
which, of course, is the application of the same excimer laser to the mid-cornea
following the creation of a corneal flap with a surgical instrument known as the
microkeratome.

The epi-LASEK procedure is almost identical to the PRK procedure, but varies in
the following way. Once the eye is anesthetized with powerful numbing drops, a few drops of a very dilute alcohol solution are applied to a central
circumscribed area on the surface of the cornea and allowed to stay in contact
with the corneal surface for about 20 - 30 seconds. This weak alcohol solution
is then rinsed off the surface of the eye. The function of the weak alcohol
solution is to loosen the epithelial layer (50 microns) and to allow it to be
peeled back in a sheet of epithelial cells, thereby exposing the underlying
Bowman's layer. This is not to be confused with LASIK, which actually uses a
microkeratome instrument to create a flap of both epithelium and the front part
of the stromal tissue measuring anywhere between 130 to 180 microns. In
epi-LASEK,
the epithelium-only layer is laid back in a similar fashion to LASIK, but
consists of only epithelium, not corneal stroma. In epi-LASEK, once the epithelial
cells have been laid out of the way, the laser is applied to Bowman's layer in
the exact same fashion as in PRK. Once the laser treatment has been completed,
the epithelial layer is laid back into place and a soft contact lens is placed
over the eye as in PRK.

Essentially, epi-LASEK and PRK are identical, except for the fact that following
the application of the laser in epi-LASEK, the epithelial cells which have been
partly devitalized by the weak alcohol solution are laid back over the treatment
area and may serve to facilitate healing of new epithelium.

Sometimes when epi-LASEK is attempted, the ultra-thin epithelium-only flap is not
strong enough to be laid back over the treatment zone. In these cases, the
epithelium will be simply wiped away as it would have been in the PRK procedure.
Thus, in this situation, the epi-LASEK becomes a PRK. If this happens it is not a
cause for concern in that it will not adversely affect the visual result. Even
if we plan and attempt epi-LASEK we cannot guarantee that the epi-LASEK will be
completed - the epithelium of each individual behaves differently.

Although similar in the acronym spelling, epi-LASEK and LASIK are not similar
procedures. Epi-LASEK and PRK are similar, the only difference is that in PRK, the
epithelium is removed completely whereas in epi-LASEK the patient's epithelium
serves as its own bandage following the procedure.

The visual results of epi-LASEK and PRK are essentially the same, as are the side
effects, risks, and complications.

It is likely that epi-LASEK will become increasingly popular for patients who
must undergo PRK. epi-LASEK will not replace LASIK.

Why should a patient have epi-LASEK versus PRK? Probably the only reasons are
slightly increased comfort following the procedure (although, in our hands, PRK
patients have not complained of discomfort in the post-operative period), and
possibly it may aid in the rapidity of the healing of the epithelium.

Although PRK has fallen out of favor over the past few years because LASIK is
so much more convenient for the patient in the early post-operative period, PRK
is gaining in popularity now with the advent of the larger optical zone lasers
capable of performing laser treatments in patients with pupils up to 9mm.
Because the depth of the treatment into the cornea increases as the treatment
diameter increases, patients with large pupils and thin corneas who desire
refractive surgery may have no choice other than to have PRK or epi-LASEK rather
than LASIK, because in LASIK, the corneal thickness required to accommodate
larger and deeper treatment zones may not be sufficient in patients with large
pupils.

In summary, PRK and epi-LASEK provide an excellent means to reduce farsightedness, nearsightedness and astigmatism.